Best apertures for maximum Dof (landscapes) with m4/3

I'm new to m4/3 coming from smaller sensor cameras where infinite dof was never a problem. Now I'm experimenting with landscape shots with my new EM5 and mostly with the panny 14/2.5 and 20/1.7 for landscapes. I shot a few with the oly 45 but that's certainly not a landscape lens. Which is the recommended apertures for maximum dof, especially for shots with a subject in the foreground like a rock or flower, while wanting to have the background in focus too. I've read that very large number apertures cause defraction and are not recommended, what can you suggest with your experience?